Clark Ashton Smith
Clark Ashton Smith was an American writer of weird horror, pulp fantasy and science fiction novels, poems and serials. He is one of "The Big Three of Weird Tales", the three men who published most prolifically in that most well-known and long-lasting of Weird Fantasy dedicated magazines, alongside the more famous H.P. Lovecraft and Robert E. Howard, author of the iconic Conan the Barbarian tales. Although he isn't as well-known as them, he had a significant impact; Clark was a co-creator for the world of Hyperborea, the primeval "lost past" world in which Robert's own Conan and King Kull Sword & Sorcery works were set, and corresponded frequently with Lovecraft, resulting in many of his weird races and deities being promoted in the latter's works.
Clark's Hyperborean tales are more obscure than Howard's, and overlap in theme if not in setting with his Poseidonis novels, set in a remnant of the sunken continent of Atlantis that avoided sinking into the ocean; his stories for both of those settings revolve around a magical culture characterized by bizarreness, cruelty, death and postmortem horrors. Averoigne is Smith's version of pre-modern France, comparable to James Branch Cabell's Poictesme, taking place in an alternate Earth where magic is very real, just illegal, and cracked down upon by the church. Zothique exists millions of years in the future. It is "the last continent of earth, when the sun is dim and tarnished". These tales have been compared to the Dying Earth sequence of Jack Vance.
He is most of interest to /tg/ for his role in inspiring Gary Gygax to write Dungeons & Dragons, as he has long been listed in the inspirations for D&D as a whole. The adventure module X2: Castle Amber invokes a cross-over between Mystara and Averoigne, Clark's writings on the necromancers of Zothique are cited as a direct inspiration in The Complete Necromancer's Handbook, and his ghoul-worshipped Great Old One, Mordiggian from Zothique became a deity in Pathfinder.